THE TONGUE. 33 



disappearing, and every filament of conferva being 

 carried up into the interior from the little area which 

 had been swept. The next instant, the foot mean- 

 while having made a small advance, the proboscis 

 unfolds again, the tongue makes another sweep, and 

 again the whole is withdrawn ; and this proceeds with 

 great regularity. I can compare the action to nothing 

 so well as to the manner in which the tongue of an 

 ox licks up the grass of the field, or to the action of 

 a mower cutting down swathe after swathe as he 

 marches along. The latter comparison is more stri- 

 king for the marks of progress which each operator 

 leaves behind him. Though the confervoid plants 

 are swept ofi' by the tongue of the Mollusk, it is not 

 done so cleanly but that a mark is left where they 

 grew; and the peculiar form and structure of the 

 tongue, which I am about to notice, leaves a series of 

 successive curves all along the course which the Mol- 

 lusk has followed, very closely like those which mark 

 the individual swathes cut by the mower in his course 

 through the field. 



The tongue, by which this operation is performed, 

 is exquisitely constructed for its work. It is indeed 

 a wonderful instrument in the complexity of its 

 armature. The appearance and position of the organ 

 would surprise any one who searched for it for the 

 first time, and as it is readily found, and as Peri- 

 winkles are no rarities, let me commend it to your 

 examination. The easiest mode of extracting it, 

 supposing that you are looking for it alone, is to slit 

 the thick muzzle between the two tentacles, when 

 the point of a needle will catch and draw out what 



